Overweight dolphins at a Japanese marine park have been put on a diet.

All 19 of the animals at Kinosaki Marine World gained weight over the summer, some as much as 22 pounds, and have been judged too unfit to perform.

Park worker Haruo Imazu is quoted as saying: "They started failing to hit jumping targets and keep upright while treading water. We were puzzled by their poor performance, and then we noticed they looked rounder."

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The weight gain has been blamed on a diet of high-calorie mackerel. They are now being fed white fish and have begun a more strenuous exercise regime.